Multiple exonucleases involved in methyl-directed MMR. When cleavage at a hemimethylated GATC is on the 3′ side of the mismatch, a 5′→3′ exonuclease is recruited, either RecJ or exonuclease VII. When cleavage is on the 5′ side of the mismatch, a 3′→5′ exonuclease is required, either exonuclease I or exonuclease X.